Flat precision electronic products such as semiconductor wafers or substrates for liquid crystal display, and the like are made by inspection steps and all kinds of fabrication steps such as painting of photo-resist, thin film deposition, creation of oxidization film or nitration film, etching and heat treatment. In these steps, the flat precision electronic products are contained in clean containers to be transported. However, since the processing times needed for each step are not the same, generally, various plans for possibly decreasing waiting time are designed. For example, in a step whose throughput speed is slow, a plurality of shelves is provided to store the clean containers temporarily. In a step whose processing time is lengthy by necessity, the shelves are divided in rows to operate in parallel. In these circumstances, clean containers, which are used in semiconductor fabrication steps, are designed in a hand-held size, and manually stored on the shelves. However, since the precision electronic products hate contaminants, such as dust, it is desirable that the containers are transported and temporarily stored not manually but automatically.
A medium or small automatic storage device for cassettes, which transports substrates for semiconductor devices, has been already proposed in Japanese Provisional Publication No. 2001-298069. This device is so constructed that two docking stations for transferring the semiconductor wafers from the cassettes are provided on the bottom, a vertical transportation space is formed therebetween, and a plurality of shelves is arranged to left and right sides of the space over the docking stations. Here, a cassette mover moving vertically and horizontally holds a cassette and transports it inside the space, and then, places it on a docking station. However, this cassette mover comprises a horizontally movable vertical strut and an end effector that holds an upper handhold (flange) of a clean container. One end of the end effector is attached below the device, and the end effector serves as an elevator. When a heavy cassette (container) is started moving or stopped just holding by a strut, a large moment of inertia acts to cause oscillation and vibration. Besides, since the oscillation and the vibration can not be easily prevented, the transport speed is not increased and the cassette can not be precisely placed on a transfer stage. Moreover, the cassette mover is constructed so as to hold a protrusion of the upper side of the cassette. Then, the top surface of the cassette is deformed so as to expand, thereby increasing the capacity of the cassette and decreasing the internal pressure thereof. Therefore, when opening a cover, dust flows into the cassette together with outside air, and conditions in the container sometimes come under the influence of the dust.
An object of the present invention is to provide an automatic device for temporarily loading, storing and unloading a container, which never affects content materials of the container by a holding means deforming the container during transportation.